Patients with well-documented chronic hepatitis C are being evaluated to determine the long-term natural history of this common form of chronic liver disease. A cohort of such patients are available to evaluate experimental therapies. Previous studies have shown that alpha interferon therapy has a short-term beneficial effect in approximately 50% of patients during treatment and that the beneficial response is sustained in approximately 20% after stopping interferon. A pilot study of ribavirin therapy indicated that this agent has an antiviral effect against hepatitis C. A randomized, placebo-controlled trial of ribavirin is currently underway.